[asm_wasm] Avoid allocating feedback vector for asm_wasm code.

A followup CL will move feedback slot allocation to the bytecode generator,
which means it won't be done for asm_wasm code and the function will have an
incorrect vector spec. Since asm_wasm doesn't use a feedback vector, just
prevent it from being allocated for this code.

BUG=v8:6921

Change-Id: I65a06f60bd75b54e5ef0df323184aad841e26177
Reviewed-on: https://chromium-review.googlesource.com/725703Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48692}

src/compiler.cc

@@ -1501,7 +1501,7 @@ void Compiler::PostInstantiation(Handle<JSFunction> function,
     }
   }
 
-  if (shared->is_compiled()) {
+  if (shared->is_compiled() && !shared->HasAsmWasmData()) {
     // TODO(mvstanton): pass pretenure flag to EnsureLiterals.
     JSFunction::EnsureLiterals(function);
 

src/objects-inl.h

@@ -4019,7 +4019,9 @@ bool JSFunction::has_feedback_vector() const {
 JSFunction::FeedbackVectorState JSFunction::GetFeedbackVectorState(
     Isolate* isolate) const {
   Cell* cell = feedback_vector_cell();
-  if (cell == isolate->heap()->undefined_cell()) {
+  if (shared()->HasAsmWasmData()) {
+    return NO_VECTOR_NEEDED;
+  } else if (cell == isolate->heap()->undefined_cell()) {
     return TOP_LEVEL_SCRIPT_NEEDS_VECTOR;
   } else if (cell->value() == isolate->heap()->undefined_value() ||
              !has_feedback_vector()) {

src/objects.cc

@@ -12286,6 +12286,7 @@ void JSFunction::EnsureLiterals(Handle<JSFunction> function) {
       break;
     }
     case HAS_VECTOR:
+    case NO_VECTOR_NEEDED:
       // Nothing to do.
       break;
   }

src/objects.h

@@ -4000,7 +4000,8 @@ class JSFunction: public JSObject {
   enum FeedbackVectorState {
     TOP_LEVEL_SCRIPT_NEEDS_VECTOR,
     NEEDS_VECTOR,
-    HAS_VECTOR
+    HAS_VECTOR,
+    NO_VECTOR_NEEDED
   };
 
   inline FeedbackVectorState GetFeedbackVectorState(Isolate* isolate) const;